Method for calibrating an irradiation device for an apparatus for additively manufacturing three-dimensional objects

ABSTRACT

Method for calibrating an irradiation device for additively manufacturing three-dimensional objects by successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, which irradiation device comprises a first and a second irradiation unit adapted to guide a first and a second energy beam, wherein at least two first and two second calibration patterns are generated, wherein the at least two first calibration patterns are generated in at least two different first positions via the first energy beam and the at least two second calibration patterns are generated in at least two different second positions via the second energy beam and position information are determined relating to the positions of the at least two first and second calibration patterns and calibration information are generated relating to a calibration status of the irradiation device based on the determined position information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Patent Application serialno. 18 211 595.6 filed Dec. 11, 2018, the contents of which isincorporated herein by reference in its entirety as if set forthverbatim.

The invention relates to a method for calibrating an irradiation devicefor an apparatus for additively manufacturing three-dimensional objectsby means of successive layerwise selective irradiation and consolidationof layers of a build material which can be consolidated by means of anenergy beam, which irradiation device comprises at least a first and asecond irradiation unit adapted to guide at least a first and a secondenergy beam.

Apparatuses for additively manufacturing three-dimensional objects andmethods for calibrating the same or calibrating components of theapparatus are generally known from prior art. For example, it is knownfrom prior art that calibrating the irradiation device that is usedduring an additive manufacturing processes for (selectively) irradiatingand thereby consolidating the build material is essential for meetingquality requirements in additive manufacturing processes. For example,it is known to determine, whether each irradiation unit of theirradiation device, e.g. comprising a beam scanner, guides therespective energy beam to the correct nominal position or whether adeviation from a nominal position occurs. Such deviations may lead toerrors in the object, e.g. stitching errors in case regions irradiatedvia a first irradiation unit and regions irradiated via a secondirradiation unit at least partially overlap or are arranged adjacent toeach other and the energy beams are not properly guided.

Usually, a calibration pattern is generated in/on a test specimen, e.g.irradiated, and the actual position of the calibration pattern relativeto a nominal position of the calibration pattern is determined. Inparticular, it is known to irradiate a first cross as a firstcalibration pattern via a first irradiation unit and a second cross as asecond calibration pattern via a second irradiation unit, wherein thefirst and second calibration pattern are generated in the same position.Subsequently, deviations between the positions of the two crosses can bedetermined and thereby, derived, whether both irradiation units areproperly calibrated or whether a deviation between the irradiationunits, e.g. the coordinate systems of the irradiation units, occurs.Such calibration patterns that are irradiated to the same position haveto be analyzed thoroughly, e.g. under a microscope by service personnel.Further, oftentimes it is hard to distinguish which of the crosses hasbeen irradiated via which irradiation unit. Therefore, the calibrationmethods currently used are cumbersome and time-consuming, wherein anautomated determination process and calibration process is notavailable.

It is an object of the present invention to provide an improved methodfor calibrating an irradiation device, wherein preferably an automatedcalibration process is provided and a calibration of the irradiationdevice over a wide area, e.g. a whole build plane, is possible.

The object is inventively achieved by a method according to claim 1.Advantageous embodiments of the invention are subject to the dependentclaims.

The method described herein is a method for calibrating an irradiationdevice for an apparatus for additively manufacturing three-dimensionalobjects, e.g. technical components, by means of successive selectivelayerwise consolidation of layers of a powdered build material (“buildmaterial”) which can be consolidated by means of an energy source, e.g.an energy beam, in particular a laser beam or an electron beam. Arespective build material can be a metal, ceramic or polymer powder. Arespective energy beam can be a laser beam or an electron beam. Arespective apparatus can be an apparatus in which an application ofbuild material and a consolidation of build material is performedseparately, such as a selective laser sintering apparatus, a selectivelaser melting apparatus or a selective electron beam melting apparatus,for instance.

The apparatus may comprise a number of functional units which are usedduring its operation. Exemplary functional units are a process chamber,an irradiation device, as described before, which is adapted toselectively irradiate a build material layer disposed in the processchamber with at least one energy beam, and a stream generating devicewhich is adapted to generate a gaseous fluid stream at least partlystreaming through the process chamber with given streaming properties,e.g. a given streaming profile, streaming velocity, etc. The gaseousfluid stream is capable of being charged with non-consolidatedparticulate build material, particularly smoke or smoke residuesgenerated during operation of the apparatus, while streaming through theprocess chamber. The gaseous fluid stream is typically inert, i.e.typically a stream of an inert gas, e.g. argon, nitrogen, carbondioxide, etc.

As described before, the invention relates to a method for calibratingan irradiation device for an apparatus for additively manufacturingthree-dimensional objects. Such an irradiation device may, as describedbefore, comprise at least two irradiation units, e.g. adapted to guide afirst and a second energy beam, e.g. laser beams, with correspondingbeam guiding elements, such as scanners, preferably movable mirrorelements. The invention is based on the idea that at least two first andtwo second calibration patterns are generated, wherein the at least twofirst calibration patterns are generated in at least two different firstpositions via the first energy beam and the at least two secondcalibration patterns are generated in at least two different secondpositions via the second energy beam. Subsequently, position informationcan be determined which position information relate to the positions ofthe at least two first and second calibration patterns, wherein based onthe determined position information calibration information can begenerated that relate to a calibration status of the irradiation device.

In other words, it is possible to generate at least two, in particularmultiple, first and second calibration patterns via the at least twoirradiation units of the irradiation device. Afterwards, it is possibleto determine the positions of the individual calibration patterns, e.g.the first calibration patterns that have been generated via the firstirradiation unit guiding the first energy beam and the secondcalibration patterns that have been generated via the second irradiationunit guiding the second energy beam. As the individual calibrationpatterns are generated in different positions and therefore, do notoverlap or are not generated in the same position, it is possible todistinguish between the individual calibration patterns and therefore,the determination and calibration process is facilitated and canpreferably be automated.

Based on the position information that relates to the position of theindividual calibration patterns, it is possible to derive calibrationinformation that indicates whether the irradiation device is properlycalibrated or whether a deviation between the nominal positions and theactual positions of the individual calibration patterns occurs. Thus, itis possible to assure that the calibration status that can be derivedfrom the calibration information based on the determined positioninformation indicates, whether a calibration of the determination deviceis necessary or whether the irradiation device is already properlycalibrated. Thus, it is possible to assure that each irradiation unit isadapted to properly guide the energy beam across the build plane, inparticular that defined nominal positions and accuracies are met andthat no deviations between the nominal positions and the actualpositions of the energy beams occur during an additive manufacturingprocess. Therefore, it is possible to avoid or prevent positioningerrors, such as stitching errors, during the additive manufacturingprocess.

The inventive method may further be improved in that at least oneparameter, preferably an irradiation parameter, of one of theirradiation units may be adjusted dependent on the generated calibrationinformation. Thus, it is possible to generate the calibrationinformation, as described before, that relates to the calibration statusof the irradiation device. For example, if a deviation occurs, e.g. oneof the calibration patterns is not generated in the correct nominalposition, a corresponding irradiation parameter of the irradiation unitused to guide the energy beam to generate the calibration pattern, canbe adjusted. For example, it is possible to use other irradiationparameters relating to the guidance of the energy beam, for examplebased on which the beam guiding unit of one of the irradiation units iscontrolled.

According to a preferred embodiment of the inventive method, multiplefirst and second calibration patterns may be generated in defined firstand second positions two-dimensionally distributed across a testspecimen, preferably equidistantly distributed. According to thisembodiment, it is possible to distribute the first and secondcalibration patterns two-dimensionally across a test specimen, whereinthe individual first and second calibration patterns are generated indefined first and second positions. Preferably, the individualcalibration patterns are equidistantly distributed two-dimensionallyacross the test specimen. As test specimen any arbitrary suitablematerial or surface can be used, e.g. a test specimen made from a metalsheet, e.g. aluminum, or a glass plate with (color) paint, a lasermarking tape or anodized aluminum plates, for instance. By generatingmultiple first and second calibration patterns distributed across thetest specimen, it is possible to generate position information anddetermine the calibration information across the entire test specimen,e.g. resembling the size of the build plane and therefore, assuring thatthe calibration of the irradiation device is properly performed for anyarbitrary position in the build plane.

Further, it is possible to determine at least two sets of positioninformation each relating to the position of at least two first and/orsecond calibration patterns and/or relating to a relative positionbetween at least one first and at least one second calibration pattern,based on the same pattern series, in particular generated in the sameprocess. Thus, it is possible to determine two sets of positioninformation based on the same pattern series, wherein the two sets ofposition information may each relate to the position of at least twofirst and/or second calibration patterns and/or may relate to a relativeposition between at least one first and at least one second calibrationpattern. Thus, it is advantageously possible, to generate multiplecalibration patterns, e.g. at least two first and second calibrationpatterns, wherein position information may be determined indicatingwhether the at least two first or at least two second calibrationpatterns are arranged in defined relative positions, e.g. spaced apartfrom each other by a defined relative distance. Of course, otherarrangements leading to a defined relative position of the calibrationpatterns are also feasible, e.g. scaled, rotated, skewed or otherwisedistorted patterns.

It is also possible to determine the relative position between the firstand the second calibration pattern or every first and second calibrationpattern. Thus, a determination can be made, whether the firstcalibration patterns that are generated via the first irradiation unitand the second calibration patterns that are generated via the secondirradiation unit are arranged in their nominal positions, e.g. spacedaway from each other by a defined relative distance or whether stitchingerrors occur. It is particularly preferred that the calibration patternsare generated in the same process, e.g. during the same irradiation stepand the corresponding position information is also determined in thesame process step in that position information relating to the positionof the first calibration patterns and other position informationrelating to the position of the second calibration patterns or therelative position between the first and the second calibration patternscan be determined in the same determination process step.

According to another embodiment of the inventive method, a referenceposition may be defined and the position for the at least one first andsecond calibration pattern may be determined relative to the referenceposition and a deviation information may be determined relating to adeviation between the determined first and second position and nominalfirst and second positions. Thus, it is possible to arbitrarily define areference position relative to which the individual positions, inparticular first and second positions, of the first and secondcalibration patterns can be determined. The reference position may beany arbitrary position on the test specimen, e.g. the first position ofthe first calibration pattern, wherein, of course any arbitrary othercalibration pattern, e.g. one of the second calibration patterns, areference marker on the test specimen, e.g. the center of the testspecimen, or the like, can be defined as reference position. Hence, theactual positions of the calibration patterns may be determined withrespect to the reference position and therefore, it is possible todetermine deviations between the actual positions of the calibrationpatterns and nominal positions of the calibration patterns in which theyshould be generated, if the irradiation device is properly calibrated.

The calibration patterns, namely the at least one first and the at leastone second calibration pattern can be of any arbitrary shape orgeometry. The at least one first or second calibration pattern may,inter alia, comprise a cross or a circle or a triangle or a line or arectangle or an octagon or an ellipsis or an L-shaped pattern or a dot.Of course, the first and the second calibration patterns may be composedof an arbitrary combination of different shapes and/or geometries.However, it is particularly preferred that each calibration patterncomprises at least one reference marker, e.g. the branch of a cross oran edge of a triangle or a rectangle, relative to which it is possibleto determine the position of the first or second calibration pattern oradjacent first or second calibration patterns. A geometry may be chosenthat simplifies the determination process, e.g. via visual inspection orvia a corresponding determination unit.

Further, the at least one first and second calibration patterns may beidentical or different. Hence, it is possible that the first calibrationpatterns comprise a different shape or geometry than the secondcalibration patterns, wherein distinguishing between the two types ofcalibration patterns can be simplified using different geometries ordifferent shapes for the different calibration patterns. For example, itis possible that the same geometry, e.g. a triangle, cross or circle isused, but different shapes, such as wider lines of the branches of across or the edges of a rectangle or the like, can be used for thedifferent calibration patterns. Of course, it is also possible that forthe first and second calibration patterns identical geometries andshapes are used.

According to another preferred embodiment of the inventive method, thecalibration status may be determined visually or via a determinationunit, preferably by determining at least one determination section, inparticular a gap, between two adjacent first and second calibrationpatterns. Hence, as described before, it is possible that thecalibration status of the irradiation device can be derived visually ordetermined via a determination unit. Advantageously, it is possible thatservice personnel may visually determine the calibration status of theirradiation device by analyzing the generated calibration patterns viaeye inspection. It is also possible that the determination unit is usedto determine the calibration status of the irradiation device, e.g. byautomatically determining the position information of the calibrationpatterns on the test specimen and thereby generating the calibrationinformation, as described before.

It is particularly preferred that at least one determination section isdetermined that is formed by at least two adjacent first and secondcalibration patterns, for example a gap arranged between a first and asecond calibration pattern. The gap may be chosen in that two adjacentcalibration patterns generated via a properly calibrated irradiationdevice are spaced away from each other by the gap, wherein the gapsimplifies the determination process, as merely the size of the gap hasto be determined, wherein a positioning error is directly linked with adeviation from a nominal gap size.

Further, the size of the gap between two facing branches of the firstand a second calibration pattern and/or the relative position and/ororientation of two facing branches of an adjacent first and secondcalibration pattern can be determined. In other words, it is possible tochoose the geometry of the first and second calibration patterns in thatthey comprise at least one branch, each, that faces the othercalibration pattern. For example, each calibration pattern may be shapedas a cross comprising four branches facing towards the surroundingcalibration patterns in the two-dimensional distribution on the testspecimen, as described before. By determining the size of the gapbetween each two facing branches of the calibration patterns that arearranged adjacent to each other and/or the relative position and/or theorientation of two of those facing branches, it is possible to determinethe calibration status of the irradiation device. For example, therelative position of the calibration patterns can be determined bydetermining the gap size, wherein displacements can be identified bylooking at the relative position of the branches, such as the alignmentof the branches. It is also possible to derive rotational errors of theirradiation device, e.g. by determining the orientation of the twofacing branches, e.g. whether there is an angle enclosed by the twofacing branches, in particular deviating from 0° or 180°, respectively.

As described before, it is possible to determine the positioninformation via a determination unit, preferably a coordinate measuringunit and/or a scanning unit, in particular a camera. Thus, it isparticularly preferred that the determination of the positioninformation is performed automatically, e.g. by scanning the individualpositions of the calibration patterns on the test specimen. For example,it is possible to use a coordinate measuring unit to determine theactual positions of the individual calibration patterns and compare theactual positions with the nominal positions. It is particularlypreferred that the determination process in which the positions of thecalibration patterns are determined can be performed in onedetermination step, e.g. by previously irradiating the individualcalibration patterns on the test specimen and subsequently determiningthe position information for each calibration pattern.

According to another embodiment, a pattern series can be generated whichcomprises at least two first and at least two second calibrationpatterns, wherein the at least two first and second calibration patternsare arranged in a line, preferably alternatingly. Hence, the at leasttwo first and the at least two second calibration patterns can bearranged on a common line, e.g. in the same row or column, on the testspecimen, wherein each calibration pattern is arranged in a definedposition. For example, it is possible to alternatingly arrange the firstand the second calibration patterns in that at least one firstcalibration pattern is surrounded by adjacent second calibrationpatterns and vice versa. Thus, it is possible to simplify thedetermination process, as the position information for the firstcalibration patterns and the second calibration patterns can bedetermined and the relative position to the adjacent other calibrationpatterns can be determined. Hence, it is possible to derive whether theindividual calibration patterns are arranged in the correct nominalposition or whether a deviation occurs.

It is also possible to generate a two-dimensional pattern series,preferably comprising multiple pattern series, wherein the first andsecond calibration patterns are arranged alternatingly in twodirections. As described before, it is possible that in the patternseries the first and the second calibration patterns are arrangedalternatingly, wherein in the two-dimensional pattern series thecalibration patterns are arranged alternatingly in two dimensions.Hence, except from the calibration patterns that are arranged on theedges of the two-dimensional pattern series, each calibration pattern issurrounded by calibration patterns of the other type, wherein, forexample with respect to the branches or other reference markers of thecalibration patterns, it is possible to directly determine whether thecalibration patterns are properly positioned and oriented or if adeviation occurs that requires a calibration of the irradiation device.

As described before, it is possible to determine position informationwhich generally relates to the positions of the first and/or the secondcalibration patterns. In particular, the position information may be ormay relate to

-   -   an overlap of the irradiation regions of the at least two        irradiation units and/or    -   an orientation of at least one irradiation unit and/or    -   a position of at least one calibration pattern and/or    -   a rotation of an irradiation region of at least one irradiation        unit and/or    -   a distortion of an irradiation region of at least one        irradiation unit and/or    -   a scaling of an irradiation region of at least one irradiation        unit.

Of course, it is also possible that the position information may relateto a deviation of each of the previously mentionedparameters/properties, e.g. a deviation from a nominal overlap of theirradiation regions of the at least two irradiation units. Hence, theposition information may indicate whether the calibration patterns aregenerated in the proper nominal position or whether a calibration of theirradiation device has to be performed. In particular, the positioninformation may indicate whether an overlap of the irradiation regionsof the at least two irradiation units is properly adjusted, i.e. theregions in which each irradiation unit is adapted to guide thecorresponding energy beam.

Further, an orientation of at least one irradiation unit and/or arotation of an irradiation region of at least one irradiation unit canbe derived from the position information. It is also possible thatoccurring distortions of irradiation regions caused by one or bothirradiation units can be derived and that the scaling of an irradiationregion can be adjusted correctly, e.g. a different scaling between thetwo irradiation regions of the two irradiation units can be identified.Hence, it is possible that the position information relates to variousparameters that may directly influence the calibration of theirradiation device. As these parameters may be determined by determiningthe position information, it is possible to assure that the irradiationdevice is properly calibrated or if a deviation from one of the nominalparameters comprised in the position information is identified, a propercalibration of the irradiation device can be performed.

Thus, it is possible to generate correction parameters based on which acalibration of at least one parameter of the irradiation device, inparticular an irradiation parameter of at least one irradiation unit,can be performed. Therefore, it is possible that by performing the stepsof determining the position information and generating the calibrationinformation, the corresponding correction parameters can be generatedthat are used to perform the calibration process. For example, if adeviation from a nominal parameter is identified, the correspondingcorrection parameter can be generated that allows for calibrating theirradiation device in that the nominal value of the correspondingparameter can be met after the calibration.

Besides, the invention relates to an apparatus for additivelymanufacturing three-dimensional objects by means of successive layerwiseselective irradiation and consolidation of layers of a build materialwhich can be consolidated by means of an energy source, which apparatuscomprises an irradiation device with at least a first and a secondirradiation unit adapted to guide at least a first and a second energybeam, wherein the apparatus comprises a calibration unit adapted togenerate at least two first and two second calibration patterns, whereinthe at least one first calibration patterns are generated in at leasttwo different first positions via the first energy beam and the at leasttwo second calibration patterns are generated in at least two differentsecond positions via the second energy beam and adapted to determineposition information relating to the positions of the at least two firstand second calibration patterns and adapted to generate calibrationinformation relating to a calibration status of the irradiation devicebased on the determined position information.

Self-evidently, all features, details and advantages described withrespect to the inventive method are fully transferable to the inventiveapparatus. In particular, the inventive method may be performed on theinventive apparatus to calibrate the irradiation device of the inventiveapparatus.

Exemplary embodiments of the invention are described with reference tothe Fig.

The Fig. are schematic diagrams, wherein

FIG. 1 shows an inventive apparatus;

FIG. 2 shows a top view on a test specimen; and

FIG. 3 shows a detail III-III from FIG. 2 .

FIG. 1 shows an apparatus 1 for additively manufacturingthree-dimensional objects, wherein in a regular mode of operation of theapparatus 1 the three-dimensional objects can be manufactured byselective irradiation and consolidation of layers of a build materialvia an energy source. The apparatus 1 comprises an irradiation device 2with two irradiation units 3, 4, wherein each irradiation unit 3, 4comprises an energy source 5, e.g. a laser source adapted to generate anenergy beam 6, 7, preferably a laser beam. In other words, the firstirradiation unit 3 is adapted to guide the energy beam 6, e.g. via afirst beam guiding unit 8, whereas the second irradiation unit 4 isadapted to guide the second energy beam 7 via a second beam guiding unit9 across a build plane 10 in which for the purpose of calibrating theirradiation device 2 a test specimen 11 is arranged.

In this exemplary embodiment, the test specimen 11 is carried via abuild plate 12 via which in a regular mode of operation non-consolidatedbuild material and the object are height-adjustably carried. Of course,the test specimen 11 can be arranged in any other arbitrary position ina process chamber 13, i.e. the chamber in which the additivemanufacturing process is performed in a regular mode of operation.Self-evidently, the inventive method is not restricted to the specificembodiment as depicted in FIG. 1 , but the inventive method may beperformed on any arbitrary additive manufacturing apparatus 1 comprisingan irradiation device 2 independent of the specific setup inside theprocess chamber 13.

For performing the inventive method for calibrating the irradiationdevice 2 of the apparatus 1, at least two first and second calibrationpatterns 14, 15 (FIG. 2 ), in particular multiple first and secondcalibration patterns 14, 15 are generated on the test specimen 11. Forthe sake of simplicity, only four calibration patterns 14, 15 aregenerated as pattern series 16 arranged in a common line on the testspecimen 11. Of course, an arbitrary number of calibration patterns 14,15 can be arbitrarily arranged on the test specimen 11. In thisexemplary embodiment, the calibration patterns 14, 15 are arrangedalternatingly in the pattern series 16.

As can further be derived from FIG. 2 , a two-dimensional pattern series20 is generated comprising pattern series 16-19. Hence, the calibrationpatterns 14, 15 may be two-dimensionally distributed across the testspecimen 11 via the individual pattern series 16-19 forming thetwo-dimensional pattern series 20. Thus, each calibration pattern 14, 15is neighbored by two, three or four calibration patterns 14, 15 of theother type. As described before, the calibration patterns 14 aregenerated via the first irradiation unit 3 guiding the first energy beam6 across the test specimen 11 and the second calibration patterns 15 aregenerated via the second irradiation unit 4 guiding the second energybeam 7 across the test specimen 11.

Although, the calibration patterns 14, 15 are shaped as crosses in thisexemplary embodiment, any arbitrary shape or geometry can be used forthe calibration patterns 14, 15. After the calibration patterns 14, 15have been generated on top of the test specimen 11, it is possible todetermine position information of the calibration patterns 14, 15. Forexample, it is possible to derive position information via eyeinspection, by comparing the positions of the calibration patterns 14,15. It is also possible to use a determination unit (not shown) that isadapted to determine the positions or the relative positions ordeviations thereof of the individual calibration patterns 14, 15.

As the calibration patterns 14, 15 are crosses comprising branches 21,each calibration pattern 14, 15 has at least two neighboring calibrationpatterns 14, 15 of the other type, wherein two branches 21 of twodifferent calibration patterns 14, 15 face each other. FIG. 3 shows twofacing branches 21 of two different calibration patterns 14, 15 asdepicted via the dashed circle in FIG. 2 . Between the two facingbranches 21 a gap 22 is enclosed, wherein it is possible to determinethe size of the gap 22 for determining the position information. Forexample, it is possible to determine whether the gap 22 has a definedsize or whether a displacement of one of the branches 21 occurs relatingto a positioning error of one of the irradiation units 3, 4corresponding to whatever branch 21 is not in the nominal position.

For example, two positioning errors are depicted in FIG. 3 , wherein adotted line 23 depicts a spatial positioning error, wherein thecalibration pattern 15, in particular the branch 21 of the calibrationpattern 15 is displaced by a distance 24 in one direction and by adistance 26 in a second direction, for example in x-direction andy-direction. By determining the relative position of the calibrationpatterns 14, 15, in particular the facing branches 21, it is possible todetermine whether the calibration patterns 14, 15 have been generated inthe correct nominal position or whether a deviation occurs.

By deriving the position information it is possible to generate acalibration information relating to whether the irradiation device 2 isproperly calibrated or whether a calibration is necessary. In the caseof the dotted line 23 a calibration is necessary, as a deviation from anominal position of the calibration pattern 15 occurs. Thus, it ispossible to generate correction parameters that allow for correcting thesecond irradiation unit 4 in that the calibration pattern 15 can begenerated in the proper nominal position.

Via a dashed line 27 a rotational error is depicted, wherein thecalibration pattern 14 is rotated through an angle 28 relative to thenominal position. As described before, it is possible to determine theorientation between the two calibration patterns 14, 15, in particularthe facing branches 21, if the angle 28 is determined, a calibration ofthe irradiation device 2 can be deemed necessary. Based on the positioninformation that can be determined from the facing branches 21 it ispossible to generate correction information allowing for performing acalibration process.

Hence, the inventive method may be performed on the inventive apparatus1.

The invention claimed is:
 1. A method of calibrating an irradiationdevice of an apparatus for additively manufacturing three-dimensionalobjects, the method comprising: generating, with a first energy beam, aplurality of first calibration patterns at respectively different firstlocations of a test specimen; generating, with a second energy beam, aplurality of second calibration patterns at respectively differentsecond locations of the test specimen; determining, with a determinationunit, position information, the position information pertaining to therespective positions of the plurality of first calibration patterns andthe plurality of the second calibration patterns, wherein determiningthe position information comprises determining a gap between (i) a firstone of the plurality of first calibration patterns and (ii) a second oneof the plurality of second calibration patterns, wherein the first oneof the plurality of first calibration patterns is adjacent to the secondone of the plurality of second calibration patterns; generating, with anapparatus for use in an additive manufacturing process, calibrationinformation based at least in part on the position information, thecalibration information pertaining to a calibration status of anirradiation device used to generate the first energy beam and/or thesecond energy beam; and adjusting, with the apparatus for use in theadditive manufacturing process, at least one irradiation parameterassociated with the irradiation device based at least in part on thecalibration information.
 2. The method of claim 1, wherein the pluralityof first calibration patterns define at least part of a first patternseries, and wherein the plurality of second calibration patterns defineat least part of a second pattern series.
 3. The method of claim 2,wherein the plurality of first calibration patterns are arranged in afirst line, and wherein the plurality of second calibration patterns arearranged in a second line.
 4. The method of claim 2, wherein theplurality of first calibration patterns and the plurality of secondcalibration patterns are arranged in an alternating sequence.
 5. Themethod of claim 2, wherein the plurality of first calibration patternsand the plurality of second calibration patterns are arranged in in afirst line having a first orientation and a second line having a secondorientation that differs from the first orientation.
 6. The method ofclaim 5, wherein the first orientation corresponds to an x-direction ina coordinate system and the second orientation corresponds to ay-direction in the coordinate system.
 7. The method of claim 2, whereinthe plurality of first calibration patterns and the plurality of secondcalibration patterns are distributed equidistantly or non-equidistantlyacross the test specimen.
 8. The method of claim 1, wherein the firstenergy beam is provided by a first irradiation unit, and the secondenergy beam is provided by a second irradiation unit.
 9. The method ofclaim 2, wherein the plurality of first calibration patterns and theplurality of second calibration patterns are generated in a sameprocess.
 10. The method of claim 1, comprising: defining, with theapparatus for use in the additive manufacturing process, a referenceposition; determining, with the apparatus for use in the additivemanufacturing process, the position information pertaining to a firstrespective one of the plurality of first calibration patterns relativeto the reference position, and determining the position informationpertaining to a second respective one of the plurality of secondcalibration patterns relative to the reference position; anddetermining, with the apparatus for use in the additive manufacturingprocess, deviation information pertaining to a deviation between thereference position and the position information.
 11. The method of claim1, wherein at least one of the plurality of first calibration patternscomprises, and/or wherein at least one of the plurality of secondcalibration patterns comprises: a cross, a circle, a triangle, a line, arectangle, an octagon, an ellipses, an L-shaped pattern, or a dot. 12.The method of claim 1, wherein at least one of the plurality of firstcalibration patterns comprises a first shape, and/or wherein at leastone of the plurality of second calibration patterns comprises a secondshape, wherein the first shape is different from the second shape. 13.The method of claim 1, wherein the gap is located between a first branchof the first one of the plurality of first calibration patterns and asecond branch of the second one of the plurality of second ofcalibration patterns.
 14. The method of claim 1, comprising:determining, with the apparatus for use in the additive manufacturingprocess, a first orientation of a first one of the plurality of firstcalibration patterns and a second orientation of a second one of theplurality of second calibration patterns.
 15. The method of claim 14,comprising: determining, with the apparatus for use in the additivemanufacturing process, the first orientation with respect to a firstfacing branch of the first one of the plurality of first calibrationpatterns and the second orientation with respect to a second facingbranch of the second one of the plurality of second calibrationpatterns.
 16. The method of claim 1, comprising: determining, with theapparatus for use in the additive manufacturing process, a spatialpositioning error as between a first one of the plurality of firstcalibration patterns and a second one of the plurality of secondcalibration patterns.
 17. The method of claim 1, comprising:determining, with the apparatus for use in the additive manufacturingprocess, the position information with a camera.
 18. The method of claim1, wherein the position information pertains to at least one of: anoverlap of a first irradiation region corresponding to a firstirradiation unit and a second irradiation region of a second irradiationunit; a first orientation of the first irradiation unit and/or a secondorientation of the second irradiation unit; a first distortion of thefirst irradiation region and/or a second distortion of the secondirradiation region; and a first scaling of the first irradiation regionand/or a second scaling of the second irradiation region.
 19. The methodof claim 1, wherein the calibration information comprises one or morecorrection parameters based on which the at least one irradiationparameter may be adjusted.